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PV wiring size

  • 29-04-2018 8:23am
    Registered Users Posts: 26 Pauldub

    Hi all,
    I have a sunnyboy 4000tl and have bought 15 axitech AC-260P/156-60S. The SMA design tool calculated wiring of 1.5 mm diameter, i have bought 4mm solar cable, but wanted to double check, its the right size, the panels are 30 mtres from garage where inverter is, looked at online calculator, the VDC for the system is 15 panels so 360vdc? , so the calculator is saying wire diameter of 1.5 mm. I intend to wire the panels in a single string, as the tool states that the max voltage is below the max the inverter can handle. All help appreciated


  • Registered Users Posts: 1,097 ✭✭✭ freddyuk

    AC-260P/156-60S VOC is 38v so string voc = 38 * 15 ?? You also need to take into account the temperature coefficient.... which will increase the VOC in colder temperatures. Inverter limit is 750v so you are within the acceptable range.
    4mm cable would be the standard acceptable size so this is correct.
    The inverter will unlikely be at best efficiency as it is oversized for the system. Normally 80% of the total installed wattage is more efficient so a 3600tl would be a closer match but I have not run the designer.

  • Registered Users Posts: 1,627 ✭✭✭ quentingargan

    If you are burying the cables in walls, solar cable might not be ideal. Under UK MCS standards, solar cable can only be used where it is visible. Otherwise it should be in separate steel trunks or SWA. See attached. This is because you cannot fuse a single string so there is no protection.

  • Registered Users Posts: 26 Pauldub

    Thank you for the replies, much appreciated. I am not burying the cable in the fabric of the garage. It will run up outside wall through flexible conduit, then in through DC Disconnect isolator, into conduit into garage, both cable into single conduit, then to inverter. Great PDF, very informative,

    I was just double checking cable size, as its very important. Thanks again

  • Posts: 0 [Deleted User]

    so there is no protection.

    The protection is the cable is rated to handle peak fault current.